RecruitingDrug trialA Study to Evaluate ALN-6400 in Healthy Volunteers and Patients With Hereditary Hemorrhagic Telangiectasia (HHT)The purpose of this study is to: * evaluate the safety, tolerability, pharmacokinetics (PK) and pharmacodynamics (PD) of single ascending doses of ALN-6400 in healthy volunteers * evaluate the efficacy, safety, tolerability and PD of multiple doses of ALN-6400 in adult patients with HHT